Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a top view of a first image of a display screen or portion thereof with transitional graphical user interface, showing our new design; and,

FIG. 2 is a top view of a second image thereof.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1 and 2. The process or period in which one image transitions to another image forms no part of the claimed design.

The broken line showing of a display screen or portion thereof is for illustrative purpose only, and forms no part of the claimed design. 

CLAIM The ornamental design of a display screen or portion thereof with transitional graphical user interface, as shown and described. 